Dementia is characterized as the loss of cognitive function having a severity so as to interfere with a person's daily activities. Cognitive function includes activities such as knowing, thinking, learning, memory, perception, and judging. Symptoms of dementia can also include changes in personality, mood, and behavior of the subject.
Dementia is a collection of symptoms that can be caused by any of a variety of diseases or conditions; it is not itself a disease. Although, in some cases, dementia can be cured by curing the underlying disease (e.g. infection, nutritional deficiency, tumor), in most cases dementia is considered incurable.
Dementia is considered a late-life disease because it tends to develop mostly in elderly people. About 5-8% of all people over the age of 65 have some form of dementia, and this number doubles every five years above that age. It is estimated that as many as half of people in their 80s suffer from some form of dementia. The most common cause of dementia is Alzheimer's disease, which affects about 4 million Americans and appears to be increasing in frequency more than most other types of dementia. Other causes of dementia include AIDS or HIV infection, Creutzfeldt-Jakob disease, head trauma (including single-event trauma and long term trauma such as multiple concussions or other traumas which may result from athletic injury), Lewy body disease, Pick's disease, Parkinson's disease, Huntington's disease, drug or alcohol abuse, brain tumors, hydrocephalus, and kidney or liver disease.
Furthermore, people suffering from mental diseases or disorders can suffer from varying levels of diminishment of cognitive function that do not rise to the level of dementia. Additionally, generally healthy individuals may also perceive some loss of cognitive function, most commonly a reduction in the function of memory. Loss or diminshment of memory may occur in any of the four commonly designated phases of memory, namely learning, retention, recall and recognition, and may be related to immediate memory, recent memory or remote memory. Loss of motor function may occur as a result of any of a number of causes, including many of those discussed above for which there is also a loss of cognitive function.
High energy laser radiation is now well accepted as a surgical tool for cutting, cauterizing, and ablating biological tissue. High energy lasers are now routinely used for vaporizing superficial skin lesions and, to make deep cuts. For a laser to be suitable for use as a surgical laser, it must provide laser energy at a power sufficient to heart tissue to temperatures over 50° C. Power outputs for surgical lasers vary from 1-5 W for vaporizing superficial tissue, to about 100 W for deep cutting.
In contrast, low level laser therapy involves therapeutic administration of laser energy to a patient at vastly lower power outputs than those used in high energy laser applications, resulting in desirable biostimulatory effects while leaving tissue undamaged. For example, in rat models of myocardial infarction and ischemia-reperfusion injury, low energy laser irradiation reduces infarct size and left ventricular dilation, and enhances angiogenesis in the myocardium. (Yaakobi et al., J. Appl. Physiol. 90, 2411-19 (2001)). Low level laser therapy has been described for treating pain, including headache and muscle pain, and inflammation.